Constraining the distribution and relationship between overpressure, natural fracture density and temperature in the Cooper Basin, Australia
David Kulikowski A , Dennis Cooke A and Khalid Amrouch AAustralian School of Petroleum, The University of Adelaide
The APPEA Journal 56(1) 11-28 https://doi.org/10.1071/AJ15002
Published: 2016
Abstract
To effectively and safely extract hydrocarbon from low permeability and overpressured reservoirs in the Cooper Basin, a thorough understanding of the regional and field scale distribution of overpressure, temperature and fracture density is essential. Previous research omitted the effect of fluid expansion and hydrocarbon generation mechanisms for overpressure generation in the basin, albeit reservoir temperatures have sharply increased in the past five million years.
The authors collate pressure (>8,000 samples) and temperature (>6,000 samples) data from 1,095 wells across the SA portion of the Cooper Basin and incorporate natural fracture densities from 28 interpreted borehole image logs to investigate the spatial variation, and potential relationship, between pressure, temperature and natural fracture density. Results show significantly lower geothermal gradients within the Patchawarra Trough, likely attributed to a lack of shallow volcanics, blanketing coals or low uranium content. Shallow volcanics are common in high-temperature areas such as the Moomba/Big Lake and Gidgealpa fields and deeper portions of the Nappamerri Trough, with overpressured wells (>0.45 psi/ft) appearing to cluster in these areas, particularly south of the Gidgealpa-Merrimelia-Innamincka Ridge. Fracture density shows no obvious relationship to pressure, inferring a dominant structural origin for natural fracture development. Although the authors cannot exclusively attribute fluid expansion and hydrocarbon expansion mechanisms to overpressure, they likely have a profound effect.
Future work should investigate the feasibility of integrating pressure, vertical stress and sonic velocity to constrain the overpressure generation mechanism within the basin while incorporating field scale seismic attribute analysis for natural fracture detection and overpressure analysis.
David Kulikowski holds a BSc (Honours) in petroleum geoscience and geophysics, and is now completing a PhD by publication in structural geology at the Australian School of Petroleum, University of Adelaide. David’s main research interests are in better understanding the structural and stress history of the Cooper Basin through the integration of micro- (calcite twinning), meso- (natural fractures) and macro-scale (faults) structural data. David is a recipient of the 2015 American Association of Petroleum Geologists (AAPG) Grants-in-Aid Foundation Scholarship. He was also a team member in the first Australian team to win the prestigious Asia-Pacific Region AAPG Imperial Barrel Award (IBA) in 2014. During the early stages of his PhD, David was employed as a part-time technical assistant at Santos in the gas production and optimisation engineering team. david.kulikowski@adelaide.edu.au |
Dennis Cooke has a PhD in geophysics from the Colorado School of Mines, and more than 25 years of experience in oil and gas exploration and development. He is a past-president of the Australian Society of Exploration Geophysicists (ASEG), and a former vice president of the Society of Exploration Geophysicists (SEG). Dennis owns and operates ZDAC Geophysical Technology, which provides technology and services for seismic inversion and reservoir characterisation. He is an Adjunct Assistant Professor at the University of Adelaide’s Australian School of Petroleum. dennis.cooke@adelaide.edu.au |
Khalid Amrouch is a Lecturer/researcher at the Australian School of Petroleum. He joined the University of Adelaide in 2013. He started his career by working for five years as a structural geologist in the IFPEN (Institut Français du Pétrole Énergies Nouvelles), and he was also a member of the crustal deformation team of the tectonic laboratory at Paris VI University (Pierre and Marie Curie). He also worked in Mines PariTech as a geologist engineer, where his main objective was to study the chronological history of fractures evolution using a field geotechnical analysis of different fracture sets. Khalid’s main research interests relate to stress/strain patterns and the understanding of the kinematics and (micro/meso) deformation mechanisms of folded and fractured sedimentary formations, timing of deformation and tectonic history. Recently he has focused his interests on fractures chronology and on the principal paleostress, and strain quantification and fracture stimulation in sedimentary rocks. khalid.amrouch@adelaide.edu.au |
